الكاتب: Multiple References

Caffeine is one of numerous substances that have been used illegally to improve the athletic performances of human and nonhuman competitors. While studies have demonstrated that caffeine is most beneficial for competitions that entail prolonged or rigorous physical activity, the cellular changes that underlie caffeine-enhanced performance remain incompletely understood. Previous studies have revealed that caffeine elicits numerous cellular and physiologic changes that could increase athletic endurance, including improvements in cardiac function (Evoniuk et al., 1987), increased skeletal muscle contractility (Sinclair & Geiger, 2000) as well as the well-recognized psychomotor stimulant effects in the central nervous system (CNS). While most evidence indicates that psychomotor stimulation derives from caffeine-induced antagonism of forebrain A1 and A2a adenosine receptors in humans and laboratory animal species (see review by Fredholm et al., 1999), it is possible that other actions may contribute to the behavioral effects of caffeine, including influences on central noradrenergic